In vitro fatty acid and lipid biosynthesis during development of insects

Abstract

1. 1. In vitro biosynthesis of fatty acids from [1- 14C]acetate, desaturation of [1- 14C] palmitic and [1- 14C]stearic acids and their incorporation into different classes of lipids have been investigated with homogenates of larvae and pharate adults of Ceratitis capitata. 2. 2. The time-course of [1- 14C]acetate incorporation shows clear differences in the behaviour of larval and pharate adult homogenates. Specific radioactivities of fatty acids synthesised by larval homogenates exhibit a net distinction between mediumchain and long-chain fatty acids. This distinction is not exhibited in the [ 14C]acetate incorporation by pharate adult homogenates. 3. 3. Both developmental stages also show differences in the incorporation of radioactivity into different classes of lipids. Triglycerides or phospholipids become rapidly labelled by either larval or pharate adult homogenates, respectively. This different behaviour of both developmental stages also applies to the specific radioactivity of the individual fatty acids present in the lipid classes. Decanoic acid has the highest specific radioactivity of the fatty acids incorporated into triglycerides by larval homogenates. The fatty acids of triglycerides from pharate adults, on the other hand, do not exhibit any incorporation of radioactivity. 4. 4. Desaturation of [1- 14C]palmitic and [1- 14C]stearic acids has been investigated in larval and pharate adult homogenates. Pharate adult homogenates do not desaturate these fatty acids, whereas larval homogenates exhibit a certain degree of desaturation. [ 14C]Palmitic and [ 14C]stearic acids are effectively incorporated by larval homogenates while they remain in a free form during incubation with pharate adult homogenate. However, stearic acid shows a lower metabolic efficiency than palmitic acid. Desaturation of palmitic acid is favoured by aerobic conditions and palmitoleic acid is preferentially incorporated into phospholipids.